WASHINGTON — A new, more aggressive effort by airport screeners aims to halt randomly selected passengers for a security check just before they step onto their departing plane, according to a government memo obtained by USA TODAY.

Scores of passengers have already been pulled aside for searches as they waited in line at airport gates for boarding calls. Each of the passengers had already passed through security checkpoints when a uniformed Transportation Security Administration (TSA) officer asked them to step out of line to check their IDs or search their carry-on bags.

Passengers can be selected at random or for suspicious behavior, according to a TSA memo dated last Thursday. The program primarily targets riskier flights, according to the memo, which doesn’t specify how flights are singled out.

The TSA says it has done occasional checks of passengers at airport gates and that the new stepped-up effort has nothing to do with any particular threat. Rather, the effort is focused on the notion that mixing up tactics makes it harder for terrorists to monitor how security works, said TSA spokesman Greg Soule.

“It serves as a random, unpredictable layer,” Soule said.

The new effort raises concerns about passengers feeling hassled and flights being delayed. “I hope the TSA can work with airports and airlines to ensure that flights that may already be late aren’t targeted,” said Christopher Bidwell, security chief for the Airports Council International trade group.

Ed Wyatt said he was waiting to board a March 6 flight from Denver International Airport to Washington-Dulles when a TSA screener “grabbed somebody out of the line, opened up his briefcase and hand-wanded him.”

“To me, it’s just stupid,” said Wyatt of Olney, Md. “Why do you have to screen someone twice?”

The motive for the program, theorizes aviation security consultant Rich Roth, is that the TSA fears that airport workers, who are not routinely screened, could sneak weapons into the secure area of an airport and give them to passengers.

Gate screening was done extensively in the months after 9/11 but was phased out in 2003 as the TSA sought to reduce passenger hassles and concentrate screening at checkpoints.

Adm. James Loy, who ran the TSA in 2002 and 2003, said screening at the gates was a visible sign of security that helped “regain confidence” of passengers who were wary of flying after 9/11.

The TSA began limited gate screening in 2007. The stepped-up effort started this year.

David Conklin of Washington, D.C., was mystified Thursday when a team of six TSA screeners showed up to check the IDs of passengers boarding a 50-seat jet flying from Raleigh-Durham International Airport in North Carolina to Washington National. “I didn’t feel reassured,” he said. “I felt, what is this next hassle I’m going to have to go through?”